Radiotherapy for treating a patient by emitting therapeutic radiation to an affected part (tumor) has been well known. A high therapeutic effect is demanded for the radiotherapy. Regarding the radiation, the dose of radiation to be emitted to a normal cell is preferably lower than the dose of radiation to be emitted to a cell of the affected part. For this reason, it is necessary to precisely emit therapeutic radiation to the affected part. A radiotherapy device that performs radiotherapy includes: an imaging system that images a transmissive image of a patient; a therapeutic radiation emitter that emits therapeutic radiation; and a driver that drives the therapeutic radiation emitter. The radiotherapy device calculates the position of the affected part based on the transmissive image, and drives the therapeutic radiation emitter by using the driver so that therapeutic radiation is emitted to the position.
A support structure for supporting the therapeutic radiation emitter and the imaging system is deflected under the weight of the support structure itself or the therapeutic radiation emitter thereof. For this reason, when the support structure is moved, the transmissive image of the patient shows another visual field deviated from the desired visual field in some cases. In this case, a user is given erroneous information when determining the position of a subject to be irradiated or when confirming the precision of position determination. It has been demanded to precisely determine the position of a subject to be irradiated and to confirm the precision of position determination.
Japanese Unexamined Patent Application, First Publication No. 2001-259059 discloses an affected-part tracking method that precisely tracks respiratory displacement of an affected part. The affected-part tracking method for tracking a displacement of the affected part is characterized in that an optical flow is calculated from transmissive images of a periphery of the affected part, flow vectors thereof are combined, and thereby calculating a motion vector of the affected part.
Japanese Patent Publication No. 4064952 discloses a radiation emitter that can properly emit therapeutic radiation to a subject to be irradiated. The radiotherapy device is a radiotherapy device for emitting therapeutic radiation to an affected part of a patient positioned at the isocenter. The radiotherapy device includes: a plurality of transmissive-image radiation generator provided on a rotation member rotatable about an rotation axis passing through the isocenter; a plurality of image detectors configured to detect transmissive image radiation emitted from each of the plurality of transmissive-image radiation generator and to detect an image of the affected part positioned between the transmissive-image radiation generators; a therapeutic radiation generator provided on the rotation member and configured to emit therapeutic radiation to the affected part; a moving means configured to move the therapeutic radiation generator with respect to the rotation member; a time-series data processor configured to calculate an estimated position of the affected part based on each of the transmissive image data imaged in chronological order by the plurality of transmissive-image radiation generator and the plurality of image detectors; an analyzer configured to calculate displacement for moving the irradiation axis of the therapeutic radiation generator to the estimated position of the affected part based on the information of the estimated position of the affected part; and a controller configured to control the moving means so as to move the irradiation axis of the therapeutic radiation generator to the estimated position of the affected part based on the information of the displacement. The controller is configured to control the plurality of transmissive-image radiation generators such that two of the plurality of transmissive-image radiation generators do not simultaneously emit the transmissive image radiation to the affected part positioned at the isocenter.
Japanese Unexamined Patent, First Publication No. 2007-236760 discloses a radiotherapy device controller that properly emits radiation to part of a moving subject. The radiotherapy device controller is a radiotherapy device controller configured to control a radiotherapy device including: a therapeutic radiation emitter configured to emit therapeutic radiation to part of the subject; a motion detector configured to detect a motion of the subject; and a driver configured to move the therapeutic radiation emitter with respect to the subject. The radiotherapy device controller includes: an affected-part database configured to correlate a set of motions with a set of positions; a motion collector configured to collect a motion from the motion detector; and an irradiation position controller configured to move, using the driver, the therapeutic radiation emitter so that the therapeutic radiation is emitted to the position of the set of positions which is correlated with the motion.